20 React Axios Interview Questions and Answers

React is a popular JavaScript library for building user interfaces. Axios is a promise-based HTTP client that works in the browser and Node.js. If you’re applying for a position that involves React and Axios, you’re likely to encounter questions about both during your interview. In this article, we review some of the most commonly asked React and Axios questions and provide tips on how to answer them.

React Axios Interview Questions and Answers

Here are 20 commonly asked React Axios interview questions and answers to prepare you for your interview:

1. What is Axios?

Axios is a promise-based HTTP client for making asynchronous HTTP requests. It works in the browser and in Node.js.

2. Can you explain the difference between HTTP and HTTPS?

HTTP is the protocol that allows communication between a web browser and a web server. HTTPS is a secure version of HTTP that uses SSL to encrypt communication between the two.

3. How can you use Axios to send an authorization header with every request?

You can use Axios to send an authorization header with every request by setting up a default header. For example:

axios.defaults.headers.common[‘Authorization’] = ‘Bearer YOUR_TOKEN’;

4. Why do you think it’s important for developers to understand how authentication works in web applications?

Authentication is important for developers to understand because it is a key security measure in web applications. By understanding how authentication works, developers can be sure that the data and resources in their applications are protected from unauthorized access. Additionally, a strong understanding of authentication can help developers troubleshoot issues related to security in their applications.

5. What are some of the most common security threats that a developer needs to be aware of when developing a web application?

There are many potential security threats that a developer needs to be aware of when developing a web application. Some of the most common include:

-SQL injection attacks
-Cross-site scripting (XSS) attacks
-Cross-site request forgery (CSRF) attacks
-Denial of service (DoS) attacks

By being aware of these potential threats, developers can take steps to mitigate them and help keep their applications secure.

6. Can you give me an example of a situation where you would want to use the GET method instead of POST?

The GET method is typically used when you are trying to retrieve data from a server, while the POST method is used when you are trying to submit data to a server. In a situation where you are trying to retrieve data from a server, you would want to use the GET method.

7. What are CORS and Cross-Origin Resource Sharing (CORS) Headers?

CORS is a mechanism that allows restricted resources on a web page to be requested from another domain outside the domain from which the first resource was served. A CORS request is an HTTP request that includes an `Origin` header. The `Origin` header indicates where the request originated from.

Cross-Origin Resource Sharing (CORS) Headers are a response header that indicates whether a request can be made from a different origin. The CORS headers allow the server to specify which origin is allowed to make the request.

8. When should you use the .then() function in Axios?

The .then() function is used when you want to execute something after the Axios request is complete. This is useful for things like updating the UI after receiving new data from the server.

9. What does the status code 200 indicate? What about 404 or 500?

The status code 200 indicates that the request was successful. The status code 404 indicates that the requested resource could not be found. The status code 500 indicates that there was an error on the server.

10. What is the main advantage of using axios over other AJAX libraries like jQuery?

The main advantage of using axios is that it is Promise-based. This means that you can take advantage of async/await in your code to make it simpler and more readable. jQuery, on the other hand, is callback-based, which can make code more difficult to read and understand.

11. Can you give me an overview of the different HTTP methods supported by Axios?

Axios supports a wide variety of HTTP methods, including the standard GET, POST, PUT, and DELETE methods, as well as more specialized methods like PATCH and OPTIONS.

12. What is the JSONP technique? Is it used by Axios? If yes, then why?

The JSONP technique is used to bypass the same-origin policy that is enforced by most browsers. By using this technique, you can request data from a server that is located on a different domain. Axios does not use this technique by default, but it does provide a way to enable it if you need to. The reason that Axios does not use JSONP by default is because it can be a security risk, since it allows for potential cross-site scripting attacks.

13. What are some situations where sending data as query params might be better than sending them via post requests?

Sending data as query params might be better in situations where the data is not sensitive and does not need to be encrypted. Additionally, query params can be cached by browsers, which can be helpful in situations where the data is not likely to change often.

14. What are the preflight requests that Axios makes while interacting with external APIs?

The preflight requests that Axios makes are designed to ensure that the external API is able to handle the request that is about to be made. This includes checking to see if the API supports the methods and headers that will be used in the request, as well as checking the credentials that will be used to authenticate the request.

15. In what situations might you want to opt out of making these preflight requests?

There are a few reasons you might want to opt out of making preflight requests. One reason is if you are making a request to a server that you know does not support CORS. Another reason is if you are making a simple request (GET, HEAD, or POST) and you are confident that the server will not reject it. Finally, you might want to opt out if you are making a request from a browser that does not support CORS.

16. What is the default timeout value set on requests made with Axios? How can this be changed?

The default timeout value for Axios is set to 0, which means that there is no timeout set. This can be changed by setting the timeout property on the Axios config object.

17. What happens if we don’t set up any handler for error responses from the server? Will our app just crash?

If you don’t set up any handler for error responses from the server, then your app will just crash. This is because the default behavior for Axios is to just throw an error when it receives an error response from the server.

18. Does Axios support file uploads?

Yes, Axios supports file uploads.

19. What are some situations where uploading files via Ajax might not work correctly?

One potential issue with uploading files via Ajax is that some browsers do not support the File API, which is necessary for reading file data. Additionally, some browsers may have security restrictions that prevent Ajax requests from accessing local files.

20. How can you configure Axios to automatically retry failed requests?

You can configure Axios to automatically retry failed requests by setting up a interceptor. An interceptor is a function that is called with Axios’ request and response objects. This function can be used to modify the request or response objects, or to handle errors. In this case, we would want to use the interceptor to check for errors and retry the request if necessary.